It is known that a polymer having at least one reactive silicon group in its molecule has a nature that the polymer is crosslinked through formation of siloxane bonds, which follows hydrolysis reaction or the like of the reactive silicon group due to moisture or the like, even at room temperature, so as to give a rubbery cured product.
Out of such polymers having a reactive silicon group, organic polymers having a main chain skeleton made of polyoxyalkylene based polymer or polyisobutylene based polymer are disclosed in JP-A-52-73998, JP-A-63-6041 and the like, and have already been industrially produced and have widely been used for sealants, adhesives, paints and the like. Curable compositions containing a polymer having a main chain skeleton made of polysiloxane, in particular, diorganopolysiloxane have also been reported in many documents such as JP-B-32-3742.
Curable compositions used for sealants, adhesives, paints and the like, and rubbery cured products obtained by curing the compositions are required to have various properties such as curability, adhesiveness, and mechanical properties.
Curable compositions containing a polymer having a reactive silicon group are cured by use of a curable catalyst. Usually, an organotin catalyst having a carbon-tin bond, such as dibutyltin bis(acetylacetonate) has widely been used. In recent years, however, about organotin compounds, the toxicity thereof has been pointed out. Thus, organotin-free catalysts have been desired to be developed.
Many researches have been made on metal carboxylates, metal alkoxides, and the like as organotin-free catalysts. Among them, carboxylic acids or amine compounds are catalysts containing no metal, and are expected to give only relatively small effects onto the environment. Patent Document 4 discloses that use of a combination of a carboxylic acid with an amine gives a curable composition having a good curability. However, in curable compositions which are cured by a silanol catalyst in which an amine compound and a carboxylic acid are used in combination, the resultant cured products cannot easily gain a sufficient adhesiveness. Thus, some of the compositions are unsuitable for sealants, adhesives and the like. As stated in JP-A-05-117519, sufficient curability is not easily obtained by use of an amine compound alone.
On the other hand, as a catalyst for producing an organopolysiloxane by hydrolyze/condensing an alkoxysilane, a compound having a Si—F bond is disclosed in JP-A-08-104753. However, this compound alone exhibits very low reactivity as a curing catalyst for a polymer having a reactive silicon group.